1/*
  2 * This program is free software; you can redistribute it and/or modify it
  3 * under the terms of the GNU General Public License version 2 as published
  4 * by the Free Software Foundation.
  5 *
  6 * Copyright (C) 2013 John Crispin <blogic@openwrt.org>
  7*/
  8
  9#include <linux/module.h>
 10#include <linux/platform_device.h>
 11#include <linux/interrupt.h>
 12#include <linux/timer.h>
 13#include <linux/of_gpio.h>
 14#include <linux/clk.h>
 15
 16#include <asm/mach-ralink/ralink_regs.h>
 17
 18#define TIMER_REG_TMRSTAT		0x00
 19#define TIMER_REG_TMR0LOAD		0x10
 20#define TIMER_REG_TMR0CTL		0x18
 21
 22#define TMRSTAT_TMR0INT			BIT(0)
 23
 24#define TMR0CTL_ENABLE			BIT(7)
 25#define TMR0CTL_MODE_PERIODIC		BIT(4)
 26#define TMR0CTL_PRESCALER		1
 27#define TMR0CTL_PRESCALE_VAL		(0xf - TMR0CTL_PRESCALER)
 28#define TMR0CTL_PRESCALE_DIV		(65536 / BIT(TMR0CTL_PRESCALER))
 29
 30struct rt_timer {
 31	struct device	*dev;
 32	void __iomem	*membase;
 33	int		irq;
 34	unsigned long	timer_freq;
 35	unsigned long	timer_div;
 36};
 37
 38static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
 39{
 40	__raw_writel(val, rt->membase + reg);
 41}
 42
 43static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
 44{
 45	return __raw_readl(rt->membase + reg);
 46}
 47
 48static irqreturn_t rt_timer_irq(int irq, void *_rt)
 49{
 50	struct rt_timer *rt =  (struct rt_timer *) _rt;
 51
 52	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
 53	rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);
 54
 55	return IRQ_HANDLED;
 56}
 57
 58
 59static int rt_timer_request(struct rt_timer *rt)
 60{
 61	int err = request_irq(rt->irq, rt_timer_irq, IRQF_DISABLED,
 62						dev_name(rt->dev), rt);
 63	if (err) {
 64		dev_err(rt->dev, "failed to request irq\n");
 65	} else {
 66		u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
 67		rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
 68	}
 69	return err;
 70}
 71
 72static void rt_timer_free(struct rt_timer *rt)
 73{
 74	free_irq(rt->irq, rt);
 75}
 76
 77static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
 78{
 79	if (rt->timer_freq < divisor)
 80		rt->timer_div = rt->timer_freq;
 81	else
 82		rt->timer_div = divisor;
 83
 84	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
 85
 86	return 0;
 87}
 88
 89static int rt_timer_enable(struct rt_timer *rt)
 90{
 91	u32 t;
 92
 93	rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
 94
 95	t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
 96	t |= TMR0CTL_ENABLE;
 97	rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
 98
 99	return 0;
100}
101
102static void rt_timer_disable(struct rt_timer *rt)
103{
104	u32 t;
105
106	t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
107	t &= ~TMR0CTL_ENABLE;
108	rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
109}
110
111static int rt_timer_probe(struct platform_device *pdev)
112{
113	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
114	struct rt_timer *rt;
115	struct clk *clk;
116
117	rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
118	if (!rt) {
119		dev_err(&pdev->dev, "failed to allocate memory\n");
120		return -ENOMEM;
121	}
122
123	rt->irq = platform_get_irq(pdev, 0);
124	if (!rt->irq) {
125		dev_err(&pdev->dev, "failed to load irq\n");
126		return -ENOENT;
127	}
128
129	rt->membase = devm_ioremap_resource(&pdev->dev, res);
130	if (IS_ERR(rt->membase))
131		return PTR_ERR(rt->membase);
132
133	clk = devm_clk_get(&pdev->dev, NULL);
134	if (IS_ERR(clk)) {
135		dev_err(&pdev->dev, "failed get clock rate\n");
136		return PTR_ERR(clk);
137	}
138
139	rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
140	if (!rt->timer_freq)
141		return -EINVAL;
142
143	rt->dev = &pdev->dev;
144	platform_set_drvdata(pdev, rt);
145
146	rt_timer_request(rt);
147	rt_timer_config(rt, 2);
148	rt_timer_enable(rt);
149
150	dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq);
151
152	return 0;
153}
154
155static int rt_timer_remove(struct platform_device *pdev)
156{
157	struct rt_timer *rt = platform_get_drvdata(pdev);
158
159	rt_timer_disable(rt);
160	rt_timer_free(rt);
161
162	return 0;
163}
164
165static const struct of_device_id rt_timer_match[] = {
166	{ .compatible = "ralink,rt2880-timer" },
167	{},
168};
169MODULE_DEVICE_TABLE(of, rt_timer_match);
170
171static struct platform_driver rt_timer_driver = {
172	.probe = rt_timer_probe,
173	.remove = rt_timer_remove,
174	.driver = {
175		.name		= "rt-timer",
176		.owner          = THIS_MODULE,
177		.of_match_table	= rt_timer_match
178	},
179};
180
181module_platform_driver(rt_timer_driver);
182
183MODULE_DESCRIPTION("Ralink RT2880 timer");
184MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
185MODULE_LICENSE("GPL");